2014-05-08

A new racket/undefined library exports undefined as the value currently produced by

(letrec ([x x]) x)

This library anticipates a future where that expression will raise an exception. The racket/undefined library will continue to offer the undefined value as a bridge between versions and as a last resort.

The drawing and GUI libraries provide improved support for high-resolution bitmaps and their use on Retina displays. For example, read-bitmap includes a #:[email protected]? option to trigger substitutions through the usual "@2x" naming convention.

Check Syntax cooperates with Typed Racket to show arrows and other Check Syntax highlighting even when there is a type error.